Extra Class License Exam Questions

Subelement E6

Circuit Components

Groups

E6A - Semiconductor materials and devices: semiconductor materials; germanium, silicon, P-type, N-type; transistor types: NPN, PNP, junction, field-effect transistors: enhancement mode; depletion mode; MOS; CMOS; N-channel; P-channel
E6B - Diodes
E6C - Digital ICs: Families of digital ICs; gates; Programmable Logic Devices (PLDs)
E6D - Toroidal and Solenoidal Inductors: permeability, core material, selecting, winding; transformers; Piezoelectric devices
E6E - Analog ICs: MMICs, CCDs, Device packages
E6F - Optical components: photoconductive principles and effects, photovoltaic systems, optical couplers, optical sensors, and optoisolators; LCDs

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Group E6A Semiconductor materials and devices: semiconductor materials; germanium, silicon, P-type, N-type; transistor types: NPN, PNP, junction, field-effect transistors: enhancement mode; depletion mode; MOS; CMOS; N-channel; P-channel

E6A01 In what application is gallium arsenide used as a semiconductor material in preference to germanium or silicon?

In high-current rectifier circuits
In high-power audio circuits
In microwave circuits
In very low frequency RF circuits

E6A02 Which of the following semiconductor materials contains excess free electrons?

N-type
P-type
Bipolar
Insulated gate

E6A03 Why does a PN-junction diode not conduct current when reverse biased?

Only P-type semiconductor material can conduct current
Only N-type semiconductor material can conduct current
Holes in P-type material and electrons in the N-type material are separated by the applied voltage, widening the depletion region
Excess holes in P-type material combine with the electrons in N-type material, converting the entire diode into an insulator

E6A04 What is the name given to an impurity atom that adds holes to a semiconductor crystal structure?

Insulator impurity
N-type impurity
Acceptor impurity
Donor impurity

E6A05 What is the alpha of a bipolar junction transistor?

The change of collector current with respect to base current
The change of base current with respect to collector current
The change of collector current with respect to emitter current
The change of collector current with respect to gate current

E6A06 What is the beta of a bipolar junction transistor?

The frequency at which the current gain is reduced to 1
The change in collector current with respect to base current
The breakdown voltage of the base to collector junction
The switching speed of the transistor

E6A07 Which of the following indicates that a silicon NPN junction transistor is biased on?

Base-to-emitter resistance of approximately 6 to 7 ohms
Base-to-emitter resistance of approximately 0.6 to 0.7 ohms
Base-to-emitter voltage of approximately 6 to 7 volts
Base-to-emitter voltage of approximately 0.6 to 0.7 volts

E6A08 What term indicates the frequency at which the grounded-base current gain of a transistor has decreased to 0.7 of the gain obtainable at 1 kHz?

Corner frequency
Alpha rejection frequency
Beta cutoff frequency
Alpha cutoff frequency

E6A09 What is a depletion-mode FET?

An FET that exhibits a current flow between source and drain when no gate voltage is applied
An FET that has no current flow between source and drain when no gate voltage is applied
Any FET without a channel
Any FET for which holes are the majority carriers

E6A10 In Figure E6-2, what is the schematic symbol for an N-channel dual-gate MOSFET?

E6A11 In Figure E6-2, what is the schematic symbol for a P-channel junction FET?

E6A12 Why do many MOSFET devices have internally connected Zener diodes on the gates?

To provide a voltage reference for the correct amount of reverse-bias gate voltage
To protect the substrate from excessive voltages
To keep the gate voltage within specifications and prevent the device from overheating
To reduce the chance of the gate insulation being punctured by static discharges or excessive voltages

E6A13 What do the initials CMOS stand for?

Common Mode Oscillating System
Complementary Mica-Oxide Silicon
Complementary Metal-Oxide Semiconductor
Common Mode Organic Silicon

E6A14 How does DC input impedance at the gate of a field-effect transistor compare with the DC input impedance of a bipolar transistor?

They are both low impedance
An FET has low input impedance; a bipolar transistor has high input impedance
An FET has high input impedance; a bipolar transistor has low input impedance
They are both high impedance

E6A15 Which semiconductor material contains excess holes in the outer shell of electrons?

N-type
P-type
Superconductor-type
Bipolar-type

E6A16 What are the majority charge carriers in N-type semiconductor material?

Holes
Free electrons
Free protons
Free neutrons

E6A17 What are the names of the three terminals of a field-effect transistor?

Gate 1, gate 2, drain
Emitter, base, collector
Emitter, base 1, base 2
Gate, drain, source

Group E6B Diodes

E6B01 What is the most useful characteristic of a Zener diode?

A constant current drop under conditions of varying voltage
A constant voltage drop under conditions of varying current
A negative resistance region
An internal capacitance that varies with the applied voltage

E6B02 What is an important characteristic of a Schottky diode as compared to an ordinary silicon diode when used as a power supply rectifier?

Much higher reverse voltage breakdown
Controlled reverse avalanche voltage
Enhanced carrier retention time
Less forward voltage drop

E6B03 What special type of diode is capable of both amplification and oscillation?

Point contact
Zener
Tunnel
Junction

E6B04 What type of semiconductor device is designed for use as a voltage-controlled capacitor?

Varactor diode
Tunnel diode
Silicon-controlled rectifier
Zener diode

E6B05 What characteristic of a PIN diode makes it useful as an RF switch or attenuator?

Extremely high reverse breakdown voltage
Ability to dissipate large amounts of power
Reverse bias controls its forward voltage drop
A large region of intrinsic material

E6B06 Which of the following is a common use of a hot-carrier diode?

As balanced mixers in FM generation
As a variable capacitance in an automatic frequency control circuit
As a constant voltage reference in a power supply
As a VHF/UHF mixer or detector

E6B07 What is the failure mechanism when a junction diode fails due to excessive current?

Excessive inverse voltage
Excessive junction temperature
Insufficient forward voltage
Charge carrier depletion

E6B08 Which of the following describes a type of semiconductor diode?

Metal-semiconductor junction
Electrolytic rectifier
CMOS-field effect
Thermionic emission diode

E6B09 What is a common use for point contact diodes?

As a constant current source
As a constant voltage source
As an RF detector
As a high voltage rectifier

E6B10 In Figure E6-3, what is the schematic symbol for a light-emitting diode?

E6B11 What is used to control the attenuation of RF signals by a PIN diode?

Forward DC bias current
A sub-harmonic pump signal
Reverse voltage larger than the RF signal
Capacitance of an RF coupling capacitor

E6B12 What is one common use for PIN diodes?

As a constant current source
As a constant voltage source
As an RF switch
As a high voltage rectifier

E6B13 What type of bias is required for an LED to emit light?

Reverse bias
Forward bias
Zero bias
Inductive bias

Group E6C Digital ICs: Families of digital ICs; gates; Programmable Logic Devices (PLDs)

E6C01 What is the function of hysteresis in a comparator?

To prevent input noise from causing unstable output signals
To allow the comparator to be used with AC input signal
To cause the output to change states continually
To increase the sensitivity

E6C02 What happens when the level of a comparator’s input signal crosses the threshold?

The IC input can be damaged
The comparator changes its output state
The comparator enters latch-up
The feedback loop becomes unstable

E6C03 What is tri-state logic?

Logic devices with 0, 1, and high impedance output states
Logic devices that utilize ternary math
Low power logic devices designed to operate at 3 volts
Proprietary logic devices manufactured by Tri-State Devices

E6C04 What is the primary advantage of tri-state logic?

Low power consumption
Ability to connect many device outputs to a common bus
High speed operation
More efficient arithmetic operations

E6C05 What is an advantage of CMOS logic devices over TTL devices?

Differential output capability
Lower distortion
Immune to damage from static discharge
Lower power consumption

E6C06 Why do CMOS digital integrated circuits have high immunity to noise on the input signal or power supply?

Larger bypass capacitors are used in CMOS circuit design
The input switching threshold is about two times the power supply voltage
The input switching threshold is about one-half the power supply voltage
Input signals are stronger

E6C07 What best describes a pull-up or pull-down resistor?

A resistor in a keying circuit used to reduce key clicks
A resistor connected to the positive or negative supply line used to establish a voltage when an input or output is an open circuit
A resistor that insures that an oscillator frequency does not drive lower over time
A resistor connected to an op-amp output that only functions when the logic output is false

E6C08 In Figure E6-5, what is the schematic symbol for a NAND gate?

E6C09 What is a Programmable Logic Device (PLD)?

A device to control industrial equipment
A programmable collection of logic gates and circuits in a single integrated circuit
Programmable equipment used for testing digital logic integrated circuits
An algorithm for simulating logic functions during circuit design

E6C10 In Figure E6-5, what is the schematic symbol for a NOR gate?

E6C11 In Figure E6-5, what is the schematic symbol for the NOT operation (inverter)?

E6C12 What is BiCMOS logic?

A logic device with two CMOS circuits per package
A FET logic family based on bimetallic semiconductors
A logic family based on bismuth CMOS devices
An integrated circuit logic family using both bipolar and CMOS transistors

E6C13 Which of the following is an advantage of BiCMOS logic?

Its simplicity results in much less expensive devices than standard CMOS
It is totally immune to electrostatic damage
It has the high input impedance of CMOS and the low output impedance of bipolar transistors
All of these choices are correct

E6C14 What is the primary advantage of using a Programmable Gate Array (PGA) in a logic circuit?

Many similar gates are less expensive than a mixture of gate types
Complex logic functions can be created in a single integrated circuit
A PGA contains its own internal power supply
All of these choices are correct

Group E6D Toroidal and Solenoidal Inductors: permeability, core material, selecting, winding; transformers; Piezoelectric devices

E6D01 How many turns will be required to produce a 5-microhenry inductor using a powdered-iron toroidal core that has an inductance index (A L) value of 40 microhenrys/100 turns?

35 turns
13 turns
79 turns
141 turns

E6D02 What is the equivalent circuit of a quartz crystal?

Motional capacitance, motional inductance, and loss resistance in series, all in parallel with a shunt capacitor representing electrode and stray capacitance
Motional capacitance, motional inductance, loss resistance, and a capacitor representing electrode and stray capacitance all in parallel
Motional capacitance, motional inductance, loss resistance, and a capacitor representing electrode and stray capacitance all in series
Motional inductance and loss resistance in series, paralleled with motional capacitance and a capacitor representing electrode and stray capacitance

E6D03 Which of the following is an aspect of the piezoelectric effect?

Mechanical deformation of material by the application of a voltage
Mechanical deformation of material by the application of a magnetic field
Generation of electrical energy in the presence of light
Increased conductivity in the presence of light

E6D04 Which materials are commonly used as a slug core in a variable inductor?

Polystyrene and polyethylene
Ferrite and brass
Teflon and Delrin
Cobalt and aluminum

E6D05 What is one reason for using ferrite cores rather than powdered-iron in an inductor?

Ferrite toroids generally have lower initial permeability
Ferrite toroids generally have better temperature stability
Ferrite toroids generally require fewer turns to produce a given inductance value
Ferrite toroids are easier to use with surface mount technology

E6D06 What core material property determines the inductance of a toroidal inductor?

Thermal impedance
Resistance
Reactivity
Permeability

E6D07 What is the usable frequency range of inductors that use toroidal cores, assuming a correct selection of core material for the frequency being used?

From a few kHz to no more than 30 MHz
From less than 20 Hz to approximately 300 MHz
From approximately 10 Hz to no more than 3000 kHz
From about 100 kHz to at least 1000 GHz

E6D08 What is one reason for using powdered-iron cores rather than ferrite cores in an inductor?

Powdered-iron cores generally have greater initial permeability
Powdered-iron cores generally maintain their characteristics at higher currents
Powdered-iron cores generally require fewer turns to produce a given inductance
Powdered-iron cores use smaller diameter wire for the same inductance

E6D09 What devices are commonly used as VHF and UHF parasitic suppressors at the input and output terminals of a transistor HF amplifier?

Electrolytic capacitors
Butterworth filters
Ferrite beads
Steel-core toroids

E6D10 What is a primary advantage of using a toroidal core instead of a solenoidal core in an inductor?

Toroidal cores confine most of the magnetic field within the core material
Toroidal cores make it easier to couple the magnetic energy into other components
Toroidal cores exhibit greater hysteresis
Toroidal cores have lower Q characteristics

E6D11 How many turns will be required to produce a 1-mH inductor using a core that has an inductance index (A L) value of 523 millihenrys/1000 turns?

2 turns
4 turns
43 turns
229 turns

E6D12 What is the definition of saturation in a ferrite core inductor?

The inductor windings are over coupled
The inductor’s voltage rating is exceeded causing a flashover
The ability of the inductor’s core to store magnetic energy has been exceeded
Adjacent inductors become over-coupled

E6D13 What is the primary cause of inductor self-resonance?

Inter-turn capacitance
The skin effect
Inductive kickback
Non-linear core hysteresis

E6D14 Which type of slug material decreases inductance when inserted into a coil?

Ceramic
Brass
Ferrite
Powdered-iron

E6D15 What is current in the primary winding of a transformer called if no load is attached to the secondary?

Magnetizing current
Direct current
Excitation current
Stabilizing current

E6D16 What is the common name for a capacitor connected across a transformer secondary that is used to absorb transient voltage spikes?

Clipper capacitor
Trimmer capacitor
Feedback capacitor
Snubber capacitor

E6D17 Why should core saturation of a conventional impedance matching transformer be avoided?

Harmonics and distortion could result
Magnetic flux would increase with frequency
RF susceptance would increase
Temporary changes of the core permeability could result

Group E6E Analog ICs: MMICs, CCDs, Device packages

E6E01 Which of the following is true of a charge-coupled device (CCD)?

Its phase shift changes rapidly with frequency
It is a CMOS analog-to-digital converter
It samples an analog signal and passes it in stages from the input to the output
It is used in a battery charger circuit

E6E02 Which of the following device packages is a through-hole type?

DIP
PLCC
Ball grid array
SOT

E6E03 Which of the following materials is likely to provide the highest frequency of operation when used in MMICs?

Silicon
Silicon nitride
Silicon dioxide
Gallium nitride

E6E04 Which is the most common input and output impedance of circuits that use MMICs?

50 ohms
300 ohms
450 ohms
10 ohms

E6E05 Which of the following noise figure values is typical of a low-noise UHF preamplifier?

2 dB
-10 dB
44 dBm
-20 dBm

E6E06 What characteristics of the MMIC make it a popular choice for VHF through microwave circuits?

The ability to retrieve information from a single signal even in the presence of other strong signals
Plate current that is controlled by a control grid
Nearly infinite gain, very high input impedance, and very low output impedance
Controlled gain, low noise figure, and constant input and output impedance over the specified frequency range

E6E07 Which of the following is typically used to construct a MMIC-based microwave amplifier?

Ground-plane construction
Microstrip construction
Point-to-point construction
Wave-soldering construction

E6E08 How is voltage from a power supply normally furnished to the most common type of monolithic microwave integrated circuit (MMIC)?

Through a resistor and/or RF choke connected to the amplifier output lead
MMICs require no operating bias
Through a capacitor and RF choke connected to the amplifier input lead
Directly to the bias voltage (VCC IN) lead

E6E09 Which of the following component package types would be most suitable for use at frequencies above the HF range?

TO-220
Axial lead
Radial lead
Surface mount

E6E10 What is the packaging technique in which leadless components are soldered directly to circuit boards?

Direct soldering
Virtual lead mounting
Stripped lead
Surface mount

E6E11 What is a characteristic of DIP packaging used for integrated circuits?

Package mounts in a direct inverted position
Low leakage doubly insulated package
Two chips in each package (Dual In Package)
A total of two rows of connecting pins placed on opposite sides of the package (Dual In-line Package)

E6E12 Why are high-power RF amplifier ICs and transistors sometimes mounted in ceramic packages?

High-voltage insulating ability
Better dissipation of heat
Enhanced sensitivity to light
To provide a low-pass frequency response

Group E6F Optical components: photoconductive principles and effects, photovoltaic systems, optical couplers, optical sensors, and optoisolators; LCDs

E6F01 What is photoconductivity?

The conversion of photon energy to electromotive energy
The increased conductivity of an illuminated semiconductor
The conversion of electromotive energy to photon energy
The decreased conductivity of an illuminated semiconductor

E6F02 What happens to the conductivity of a photoconductive material when light shines on it?

It increases
It decreases
It stays the same
It becomes unstable

E6F03 What is the most common configuration of an optoisolator or optocoupler?

A lens and a photomultiplier
A frequency modulated helium-neon laser
An amplitude modulated helium-neon laser
An LED and a phototransistor

E6F04 What is the photovoltaic effect?

The conversion of voltage to current when exposed to light
The conversion of light to electrical energy
The conversion of electrical energy to mechanical energy
The tendency of a battery to discharge when used outside

E6F05 Which describes an optical shaft encoder?

A device which detects rotation of a control by interrupting a light source with a patterned wheel
A device which measures the strength of a beam of light using analog to digital conversion
A digital encryption device often used to encrypt spacecraft control signals
A device for generating RTTY signals by means of a rotating light source

E6F06 Which of these materials is affected the most by photoconductivity?

A crystalline semiconductor
An ordinary metal
A heavy metal
A liquid semiconductor

E6F07 What is a solid state relay?

A relay using transistors to drive the relay coil
A device that uses semiconductors to implement the functions of an electromechanical relay
A mechanical relay that latches in the on or off state each time it is pulsed
A passive delay line

E6F08 Why are optoisolators often used in conjunction with solid state circuits when switching 120VAC?

Optoisolators provide a low impedance link between a control circuit and a power circuit
Optoisolators provide impedance matching between the control circuit and power circuit
Optoisolators provide a very high degree of electrical isolation between a control circuit and the circuit being switched
Optoisolators eliminate the effects of reflected light in the control circuit

E6F09 What is the efficiency of a photovoltaic cell?

The output RF power divided by the input DC power
The effective payback period
The open-circuit voltage divided by the short-circuit current under full illumination
The relative fraction of light that is converted to current

E6F10 What is the most common type of photovoltaic cell used for electrical power generation?

Selenium
Silicon
Cadmium Sulfide
Copper oxide

E6F11 What is the approximate open-circuit voltage produced by a fully-illuminated silicon photovoltaic cell?

0.1 V
0.5 V
1.5 V
12 V

E6F12 What absorbs the energy from light falling on a photovoltaic cell?

Protons
Photons
Electrons
Holes

E6F13 What is a liquid crystal display (LCD)?

A modern replacement for a quartz crystal oscillator which displays its fundamental frequency
A display utilizing a crystalline liquid and polarizing filters which becomes opaque when voltage is applied
A frequency-determining unit for a transmitter or receiver
A display that uses a glowing liquid to remain brightly lit in dim light

E6F14 Which of the following is true of LCD displays?

They are hard to view in high ambient light conditions
They may be hard view through polarized lenses
They only display alphanumeric symbols
All of these choices are correct